Nearly all phenotypic features can be understood as adaptations to particular evolutionary challenges. Gould and Lewontin (1979) derisively referred to this dogma as the Panglossian paradigm of the adaptationist programme in evolutionary biology.
preadaptation; exaptations
Nearly all phenotypic features can be understood as adaptations to particular evolutionary challenges. Gould and Lewontin (1979) derisively referred to this dogma as the Panglossian paradigm of the adaptationist programme in evolutionary biology.
According to Stephen Gould and Richard Lewontin, many organismal traits are functionally suboptimal because they may have evolved originally to serve entirely different functions (or perhaps no particular function at all). An example might be the feathers that now support avian flight but were selectively favored at the outset for their role in thermoregulation. Another example might involve the lungs of primitive fish that eventually evolved into a gas bladder that now regulates buoyancy in modern fish. Yet another example might be a mobile element (see Chapter 24) that has proliferated for selfish reasons (see Chapter 48) but later became coopted by the cell for some useful role in genetic regulation for the host organism.
In 1982, Gould and Vrba coined the term “exaptation” to refer to situations in which: (1) a trait previously shaped by natural selection for a particular function is coopted for another use; or (2) a trait whose origin cannot be ascribed to the direct action of natural selection later becomes coopted for its current utility. The authors viewed a focus on exaptations to be a useful and needed conceptual counterbalance to standard adaptive explanations for many organismal features. In other words, phenotypic evolution involves a lot of what Francois Jacob (1977) had called evolutionary tinkering.
This new paradigm gets high marks for its veracity and for the eloquence with which it was presented by Gould and Lewontin, but much lower marks for its level of originality. Long before the term exaptation was introduced, evolutionary biologists routinely used the term preadaptation to refer to traits that had been coopted during evolution for some biological function other than that provided by the original. The word preadaptation became outmoded, however, because it could be misinterpreted to imply the operation of some sort of teleological process that would be contrary to evolutionary principles.
1. Schmalhausen II. Factors of Evolution The Theory of Stabilizing Selection Philadelphia, PA: Blakiston; 1949.
2. Jacob F. Evolution and tinkering. Science. 1977;196:1161–1166.
3. Gould SJ, Lewontin RC. The spandrels of San Marco and the panglossian paradigm: a critique of the adaptationist programme. Proc R Soc Lond B. 1979;205:581–598.
4. Gould SJ, Vrba E. Exaptation – a missing term in the science of form. Paleobiology. 1982;8:4–15.
5. Buss DM, Haselton MG, Shackelford TK, Bleske AL, Wakefield JC. Adaptations, exaptations, and spandrels. Amer Psychol. 1998;53:533–548.